Calculating centripetal force when radius is unknown

In summary, the conversation discusses the calculation of centripetal force for a ball with a known mass and acceleration. However, since the radius is unknown, the formula for centripetal force (F = mv^2/r) cannot be used. The question is raised as to why the equation is being rewritten when both velocity and radius are unknown.
  • #1
BogMonkey
76
0
Heres the question
"A ball with a mass of 250 g has a centripetal acceleration of 5 m/s2. What is the centripetal force acting on this ball? "

Since radius depends on the string length I have no idea how to derive it from these 2 variables. The only formula I know for getting centripetal force is F = m * V^2 / r
 
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  • #2
If the acceleration is already given why do you want to calculate it?
 
  • #3
bp_psy said:
If the acceleration is already given why do you want to calculate it?

Precisely. Elaborating, one rewrites the equation (F=ma) in that form (F=mv^2/r) because usually one knows velocity and radius. In this case, you know neither, so why rewrite it at all? :)
 

FAQ: Calculating centripetal force when radius is unknown

1. What is centripetal force?

Centripetal force is the force that keeps an object moving in a circular path. It is always directed towards the center of the circle and is necessary for an object to maintain its circular motion.

2. How is centripetal force calculated?

The formula for calculating centripetal force is Fc = (m * v^2) / r, where Fc is the centripetal force, m is the mass of the object, v is its velocity, and r is the radius of the circle.

3. What happens if the radius is unknown?

If the radius is unknown, the centripetal force cannot be accurately calculated. In this case, other factors such as the object's velocity and mass can be measured and used to find the radius using the formula r = (m * v^2) / Fc.

4. Can the centripetal force be negative?

No, the centripetal force cannot be negative. It is always directed towards the center of the circle, so it will have a positive value. However, its direction can be positive or negative depending on the direction of the velocity of the object.

5. How does the radius affect the centripetal force?

The centripetal force is directly proportional to the radius of the circular path. This means that as the radius increases, the centripetal force also increases, and vice versa. A larger radius requires less force to keep the object in circular motion, while a smaller radius requires a greater force.

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